Present diagnostic methods are inadequate to demonstrate the existence, site and extent of a suspected myocardial infarction. A non- invasive technique of imaging an infarct or ischemia by Nuclear Medicine would be ideal. This proposal outlines an approach to this end based on an analysis of pilot studies with thallium-201. Tl-201 taken up by the myocardium gives clear scintiphotos of the normal myocardium and permits an infarct to be visualized as a "cold area". A production method for Tl-201 is available on the Brookhaven Linac Isotope Producer (BLIP). Purification has been accomplished using small amounts produced by the BNL 60" cyclotron. Much of the complex interdisciplinary expertise needed to achieve infarct visualization is available at Brookhaven. We are able to label biogenic amines, for instance dopamine with C11. We have recently developed a new route to norepinephrine which utilizes HCN and which has been successfully used in the synthesis of C11-labeled nor-epinephrine from C11-labeled HCN. This material has been produced in the carrier free state thus avoiding toxicity problems. Experiments on mice have shown a very high uptake in the heart. We intend to label other pharmacologically active agents with C11, I123, and F18. We intend to evaluate rubidium-82 using an Sr82-Rb82 generator. The evaluation of diverse radiopharmaceuticals, as well as imaging techniques, necessitates the following experimentation: distribution in various organs of the radiopharmaceutical as a function of time, in a large number of different species of small animals -- mice, rats, and rabbits; the imaging of large animals' hearts before and after production of infarcts; the imaging of the beating heart with "stroboscopic slowing" with and without infarction; and the heart of the sacrificed animal to be imaged with and without infarction in and out of the body; with histological, angiographic and quantitative isotopic verification.